5.2.10 Window background manipulation routines

Procedure: bkgdset!win ch

The bkgdset! routine manipulates the background of the named
window. The window background is set to the rendered complex
character ch. The attribute part of the ch is combined
(logior’d) with all non-blank characters that are written into
the window with addch. Both the character and attribute parts
of the ch are combined with the blank characters. The
background becomes a property of the character and moves with the
character through any scrolling and insert/delete line/character
operations.

To the extent possible on a particular terminal, the attribute part of
the background is displayed as the graphic rendition of the character
put on the screen.

The return value is undefined.

Procedure: bkgdwin ch

The bkgd function sets the background property
of the current or specified window and then applies this setting to
every character position in that window: The rendition of every
character on the screen is changed to the new background rendition.
Wherever the former background character appears, it is changed to the
new background character.

The return value is undefined.

Procedure: getbkgdwin

The getbkgd function returns the given window’s current background
rendered character.